Your baby has now reached that stage when his sensory abilities would be quite advance. He would respond to sounds made from the television. Count it a as a positive sign and encourage your baby to respond to those sounds.
What you need to know
As a parent, you need to take out time during a day when you can sit with your baby and watch television. Observe his responses to various sounds. Offer your baby with a variety of shows related to cartoons, animals, education, etc. Pick up two or three sounds and ask your baby to imitate it.